Dependence of the OH concentration on solar UV

OH and the major parameters determining its concentration were measured dur ing a field campaign in August 1994 at Mankmoos, a rural, relatively unpoll uted site in northeastern Germany. The measured OH concentrations were prev iously shown to depend mainly on the intensity of solar UV and on the mixin g ratio of NO2, In this paper we develop a simple parameterization of the d ependence on solar UV and on NO2, The photolysis of O-3 to (OD)-D-1, of NO2 to NO, and of HCHO to HCO and H, all contribute significantly to the total dependence of OH on solar UV. We demonstrate that the photolysis frequency of O-3, J(O1D), is a. suitable measure for that dependence which is slight ly less than linear. The highly nonlinear dependence of OH on NOx is approx imated by a Pade function. The parameterization provides a tool for a futur e quantitative intercomparison of the measured and modeled dependences of O H on UV and NO2, It also allows the removal of the variation in the measure d OH induced by the dependences on the variables, UV and NO2, and thus enab les a search for dependences on other, less influential parameters.